1. Field of the Invention
The present invention relates to a plasma display panel and, particularly, to a structure of a surface-discharge type color plasma display panel having reduced power consumption and a fabrication method of the same color plasma display panel.
2. Description of the Prior Art
As a flat display panel whose display area can be increased easily, attention has been paid to a plasma display panel (PDP). Particularly, the color PDP has been used in a personal computer, a display of workstation and a wall television, etc. A surface-discharge type color PDP among such color PDPs is constructed with a first glass substrate equipped with electrode pairs, which are covered by a dielectric layer and each of which includes a pair of electrodes opposing mutually in a plane to form a discharge space therebetween, and a second glass substrate arranged in an opposing relation to the first glass substrate through discharge gas. Visible display is realized by applying a voltage between the electrodes of each electrode pair to generate discharge therebetween and irradiating a fluorescent member formed on an inner surface of the PDP with ultraviolet ray generated by the discharge.
A portion of a conventional surface-discharge type color PDP, which corresponds to one discharge cell thereof, is shown in FIGS. 20A, 20B and 20C, which are a plan view of the discharge cell of the conventional surface-discharge type PDP, a cross section taken along a line A-Axe2x80x2 in FIG. 20A and a cross section taken along a line C-Cxe2x80x2 in FIG. 20A, respectively,
As shown in FIGS. 20A, 20B and 20C, sustaining electrodes 712, which become electrode pairs, are formed on one and the same surface of the first glass substrate 711 and are covered by a dielectric layer 724 of a low melting point glass material and a protective film 715 formed of magnesium oxide (MgO), etc.
Thickness of the dielectric layer 724 formed on the sustaining electrodes 712 is usually uniform substantially. When the dielectric layer 724 is made thick in order to improve the light emitting efficiency of the PDP, the discharge sustaining voltage is increased. On the contrary, when the dielectric layer 724 is made thin in order to restrict the discharge sustaining voltage, the light emitting efficiency is lowered.
In order to solve such contradiction, JP 2000-113827A propose two examples of a structure of a surface-discharge type color PDP, which will be described briefly with reference to FIGS. 21A and 21B.
As shown in FIG. 21A or 21B, thickness of a dielectric layers 824 or a dielectric layer 924 is changed within a discharge cell such that a portion of the dielectric layer 824 or 924 in a location opposing to a sustaining electrode 812 or 912 becomes thinnest.
However, it is generally difficult to control the thickness of the dielectric layer 824 or the dielectric layer 924 throughout the panel. Since a variation of thickness of the dielectric layer affects discharge characteristics of the panel, it is difficult to obtain a PDP having desired display characteristics.
An object of the present invention is to provide a surface-discharge type color PDP having desired display characteristics.
Another object of the present invention is to provide a surface-discharge type color PDP capable of improving light emitting efficiency and realizing a reduction of power consumption.
Another object of the present invention is to provide a method for fabricating a surface-discharge type color PDP.
The present invention is applicable to a surface-discharge type color PDP comprises a first substrate having a plurality of electrode pairs covered by a dielectric layer, a second substrate arranged in an opposing relation to the first substrate with a gap and discharge gas filling the gap between the first substrate and the second substrate in which discharge is generated in the discharge gas by applying a voltage between the electrode pair in each discharge cell. The present invention has a basic structure in which at least one of electrodes of each electrode pair is divided in a thickness direction of the dielectric layer such that a lower electrode and an upper electrode are formed, which are electrically connected to each other to make the upper and lower electrodes equipotential.
The above mentioned basic construction of the surface-discharge type color PDP of the present invention is expansive in various manners to be described below.
In a first aspect of the surface-discharge type color PDP according to the present invention, both the electrodes of the sustaining electrode pair covered by the dielectric layer are spatially separated in the thickness direction of the dielectric layer. The spatially separated sustaining electrodes are electrically connected each other.
On the first substrate on which the discharge sustaining electrode pairs are formed, one electrodes and the other electrodes of the electrode pairs extend in parallel to each other and the plurality of the electrode pairs extend in parallel with a space therebetween.
In such surface-discharge type PDP, each of the electrode of each electrode pair includes an upper electrode and a lower electrode, the upper electrode of one electrode of the electrode pair is provided in a plurality of different layers and the upper electrodes of the other electrode of the electrode pair are provided in the same number of different layers and corresponding ones of the electrode layers of the upper electrodes are in the same position in the thickness direction of the dielectric layer. In such construction, the one of the opposing upper electrodes and the other of the opposing upper electrodes are formed symmetrically about a center of a first sustain gap between one of the lower electrodes of each electrode pair and the other lower electrode.
Furthermore, a second sustain gap may be provided between one of the upper electrodes and the other upper electrode, which are mutually opposing with a gap therebetween, which gap is the smallest among gaps between the upper electrodes of the electrode pair, and the second sustain gap is substantially coincident with the first sustain gap. Alternatively, a second sustain gap is provided between one of the upper electrodes and the other upper electrode, which are mutually opposing with a gap therebetween, which gap is the smallest among gaps between the upper electrodes of the electrode pair, and one of the first sustain gap and the second sustain gap is within the other sustain gap.
When the upper electrodes of the electrodes constituting the electrode pair are arranged in a single layer and the sustaining second region is within the first sustain gap, the upper electrodes are within the first sustain gap.
When the upper electrodes of the one and the other electrodes of the electrode pair are arranged in a single layer, the second sustain gap may be coincident with the first sustain gap or the first sustain gap is within the second sustain gap.
Alternatively, a center of said first sustain gap may be deviated from a center of said second sustain gap.
Alternatively, when the upper electrodes of the electrodes constituting the electrode pair are in a single layer, respectively, either one of the upper electrodes may be within the first sustain gap.
The surface-discharge type color PDP of the present invention may be constructed such that each of the electrodes of each electrode pair includes the lower electrode and the upper electrode and at least one divided electrode having a potential equal to the potential of one of the upper electrodes is provided on a side of the one upper electrode corresponding to at least one of the lower electrodes in a plane, which is the same as a plane of the one upper electrode, remote from the other lower electrode.
In the above-mentioned PDP, a width of the upper electrode is a half of a width of the lower electrode or less. Alternatively, the width of the upper electrode may be one-fifth the width of the lower electrode or less.
The PDP of the present invention may further comprise a connecting wiring for electrically connecting the upper electrode to the lower electrode to make the upper and lower electrodes equipotential and a low resistance wiring for leading the upper electrode together with the lower electrode externally. The PDP having such construction may further comprise partition walls formed on the second substrate extending in parallel in a direction orthogonal to the electrode pairs formed on the first substrate, wherein the first substrate includes discharge cell regions uniformly partitioned by the partition walls and regions for separating the plurality of the electrode pairs and the connecting wiring is formed in a region of each the discharge cell region except the second sustain gap between the upper electrodes corresponding to the electrode pair. The connecting wiring may be formed in regions opposing to the partition walls.
Preferably, the low resistance wiring extend in parallel to the electrode pairs on the first substrate along a line separated from the electrode pairs. The upper electrodes are formed of an electrically conductive material containing a metal or metal particles as a main constituent.
The low resistance wiring may be formed of the same material as that of the upper electrodes. Moreover, the upper electrode may be thinner than the lower electrode as well as the low resistance wiring.
The low resistance wiring may be formed of a material different from the material of the upper electrode.
In the surface-discharge type PDP in which the upper electrode is connected to the lower electrode by the connecting wiring to make the upper and lower electrodes equipotential and the upper electrode is connected externally together with the lower electrode by the low resistance wiring, the low resistance wiring may be formed either on the substrate on which the lower electrodes are formed or in a level of the upper electrode in a thickness direction of the dielectric layer.
The low resistance wiring may be formed on the substrate on which the lower electrodes are formed and in a level of the upper electrode in a thickness direction of the dielectric layer. The low resistance wiring and the connecting wiring may be formed simultaneously.
In the PDP of the present invention, the upper electrode may be formed in a single layer and the dielectric layer may include a first dielectric layer deposited on the substrate and underlying the upper electrodes and a second dielectric layer covering the substrate having the first dielectric layer. In this PDP, the upper electrodes may constitute a single layer upper electrode pair corresponding to the electrode pair and the dielectric layer is formed below the second sustain gap between the upper electrode pair such that the dielectric layer contains the second sustain gap.
According to the present invention, the discharge gas contains at least one of xenon (Xe), krypton (Kr), argon (Ar) and nitrogen (N2) as exciting gas for generating ultraviolet light for exciting a fluorescent member and a partial pressure of the exciting gas is 100 hPa or higher when the exciting gas contains one of Xe, Kr, Ar and N2.
Furthermore, a method for fabricating a PDP, according to the present invention comprises the steps of forming a first electrode pair constituting lower electrodes on a surface of a first substrate, forming a first dielectric layer covering at least a first sustain gap between the first electrode pair, forming a second electrode pair constituting upper electrodes on the first dielectric layer, depositing a second dielectric layer covering the first substrate including the first dielectric layer, arranging the second substrate in an opposing relation to the first substrate with a gap therebetween and filling the gap with discharge gas.
In such method for fabricating a PDP, the step of forming the first dielectric layer may be performed by patterning the first dielectric layer such that the first dielectric layer covers at least the first sustain gap.
The step of forming the first dielectric layer covering at least the first sustain gap between the first electrode pair may be performed by screen printing.
The first and second dielectric layers are formed of glass materials and the softening point of the glass material forming the second dielectric layer is lower than that of the glass material of the first dielectric layer.
The method for fabricating the PDP may further comprise, between the step of forming the first electrode pair, which becomes the lower electrode, on the surface of the substrate and the step of forming the second electrode pair on the first dielectric layer, which becomes the upper electrodes, the step of forming a first electrode wiring for reducing a resistance of a connecting wiring of the first electrodes.
The method for fabricating the PDP may further comprise, after the step of forming the second electrode constituting the upper electrode on the first dielectric layer, the step of forming a second electrode wiring for reducing a resistance of a lead wiring of the second electrodes.
The fabrication method may further include the step of forming a connecting wiring for connecting the second electrode to the first electrode corresponding to the second electrode after the step of forming the second electrode on the first dielectric layer.
This method may further include, after the step of forming the second electrode on the first dielectric layer, the step of simultaneously forming the connecting wiring for connecting the second electrode to the first electrode corresponding to the second electrode and a common electrode wiring for reducing a resistance of lead wiring of the first electrode and the second electrode.
The step of forming the second electrode on the first dielectric layer is performed by forming connecting wiring for connecting the second electrode to a first electrode corresponding to the second electrode and a common wiring for reducing a resistance of lead wiring of the first electrode and said second electrode, simultaneously with the formation of said second electrode.
The connecting wiring may be formed of a metal or metal particles. When the upper electrode takes in the form of a transparent conductive film, the connecting wiring may be formed of the same material as that of the upper electrode.